1. Field of the Invention
The present invention relates to a pressure control valve, particularly to a solenoid pressure control valve controlling fluid pressure corresponding to electric level. Typical types of solenoid pressure control valve are a diaphragm type receiving a feedback pressure on the diaphragm, and a spool type receiving the feedback pressure on a spool end. The present invention relates to both types of pressure control valve, particularly to the structure of magnetic section.
2. Description of the Prior Art
A pressure control valve, as shown in the United States Pat. No. 4,535,816, has a pressure modulating section, and a magnetic section having a coil assembly, a core and a rod being placed coaxially with, and pressed by a spring toward the modulating section. And a spring is attached to a plunger. The above elements are installed concentrically from outside to the center, and the magnetic section has a sealed structure. One end of the rod is supported by a leaf spring held between the case and the pressure modulating section, and the leaf spring has a through hole in the center. Another end of the rod is supported to slide in a bush which is screwed to the core.
In the above stated pressure control valve, though entering of foreign materials into the magnetic section is prevented due to the sealed structure of the magnetic section, when the movable section having the plunger and the rod moves by electrical signals no room is available for volume change. This causes worse response of the magnetic section, and precision of pressure modulation becomes worse because of pressure change or temperature change caused by the above volume change in the magnetic section.
As another end of the rod is supported by sliding method, friction of sliding makes response and precision worse.